1. Field of the Invention
The present invention relates to a high-temperature and high-pressure corrosion-resistant process heat exchanger, which decomposes sulfite (SO3) using heat from a high-temperature gas-cooled reactor to thereby produce sulfide (SO2) and oxygen (O2).
2. Description of the Related Art
Heat produced from the core of a very-high-temperature gas-cooled reactor, that is, a nuclear reactor, is transmitted to an intermediate heat exchanger using helium, and then helium or a similar second system coolant transmits the heat of the intermediate heat exchanger to a process heat exchanger.
The heat from the process heat exchanger evaporates sulfuric acid (H2SO4) to produce sulfite (SO3), and then decomposes sulfite (SO3) to produce sulfide (SO2).
A system located between the very-high-temperature gas-cooled reactor and the intermediate heat exchanger is defined as a first system, and a system located between the intermediate heat exchanger and the process heat exchanger is defined as a second system. Further, a system that produces hydrogen (H2) using heat from the process heat exchanger is defined as a third system.
Generally, when one of the processes for producing hydrogen using heat generated from the nuclear reactor, i.e. an iodine-sulfuric acid (H2SO4) decomposition process, is implemented, the process heat exchanger is required for heat transmission.
In order to produce hydrogen using temperatures of 900° C. or higher generated in the nuclear reactor, two processes are required, one of which is a process of decomposing sulfuric acid (H2SO4) into water (H2O) and sulfite (SO3), and the other of which is a process of decomposing sulfite (SO3) into sulfide (SO2) and oxygen (O2) at a temperature of about 900° C. or higher.
A sulfite (SO3) decomposer, which is one of these process heat exchangers, is a heat exchanger that is operated under severe conditions, specifically, that must generally be operated at a high temperature of 900° C. or higher, that must be able to withstand a differential pressure between two loops, and that must be resistant to corrosion. This heat exchanger cannot employ an existing heat exchanger due to these temperature and corrosion conditions, and thus a solution is being developed all over the world at present.
There is a super alloy that can be used at high temperatures but not for a long time in a SO3 atmosphere due to corrosion.
At present, it is reported that there is no process heat exchanger that can carry out an SO3 decomposition reaction and realize long-term reliability at a high temperature of 900° C. or higher anywhere in the world.
In Japan, a process heat exchanger that can be used in a sulfuric acid (H2SO4) atmosphere at a temperature of 900° C. or higher using SiC ceramic, which has good corrosion resistance, is being developed, but there are many technical difficulties from the viewpoint of the production of the ceramic itself.
Further, in Europe, an attempt is being made using high-temperature metal materials. The high-temperature metal materials have no problem from the viewpoint of the production thereof, but have a problem in that the lifespan thereof is very short due to its low corrosion resistance.